Abstract

The study was conducted in five local government areas of Benue state, Nigeria; to asses herd size and herd structure of the savanah muturu in relation to genetic improvement. A field study of the Savanah muturu herds were conducted. The mean herd sizes of the savanah muturu were 3.00 ± 0.43, 3.60 ± 0.73, 6.00 ± 2.00, 4.27 ± 0.67, 3.00 ± 2.00. In all the populations, the number of heifers and breeding bulls were low. The number of breeding females were equally low, calf crop were low and there were no heifers for replacement in all the herds. It is evident that allelic drift through random sampling will reduce heterozygosity in these populations. Fertility and other fitness related traits would also be reduced in these populations. Genetic improvement through selection would be practically impossible in these populations, as selection intensities would be too low to exert any improvement on deserve alleles and genotypes.

Keywords

Herd-size, Herd-structure, Genetic-improvement, Savanah- muturu.

Introduction

The ratio between new born males and females in a herd
determines herd size and structure is approximately one to one
[1]. However, among the mature animals the ratio is generally
much biased in favor of females. In Kalamoja, the proportion
was found to be in the range of 49 to 85 percent [2]. Meadows [3]
reported three reasons for high male calf mortality in the Kenyan
district of Kajiado. It was noted that male calves are slaughtered
at an early age: to save milk for human consumption, to reduce
stress on the dam by a suckling calf, this is especially true during
the dry season, to have meat available in manageable quantities
for the family. A large number of studies have been concerned
with the possible effect of the size of the herd on the pregnancy
rate, it was concluded by most investigators that the pregnancy
rate decreased with the size of the herd [1-6]. On the interval
between parturition and conception, it was reported by De Kruit
[6] that this interval is shorter in larger herds than in small
herds, because insemination is started sooner after parturition
in larger herd. This shorter interval between parturition and first
insemination might account in part for the higher pregnancy
rates recorded in the larger herds. Hewett [7] showed that repeat
breeders are more common in the larger herds than in small
herds. In the very small herds 8.5% of the animals failed to
become pregnant after as many as three inseminations whereas
this proportion was 13.1 in the larger herds. The number of
agonistic interactions per hour in a herd was found by Miller
and Wood–Gush [8] to be 1.1 at pasture and 9.5 at much greater
density indoors. As herd size increases there are usually more
occasions when re-grouping of animals occurs [9-11].

The muturu traits have been evaluated in a communal
management system in some states. This system has been
largely responsible for the conservation of the muturu [12]
under the system; cattle belonging to various owners in a village
are herded together. This system was developed to minimize
damage to crops by these cattle and owners. Performance traits of muturu were also evaluated with no tsetse control. Muturu
cattle improved its performance under field station compared
to the traditional system with no tsetse control. The calving
rate under the traditional system was reported as 57 percent as
against 92 percent under field station. Muturu calved early 635
day compared to 761 days and 684 days for Zebu and its crosses
respectively [13]. Muturu cattle are fertile producing viable
calf per year [14,15]. The calving interval was 18-24 months
under improved management. The animals under a tsetse free
environment were found to perform better than those in a tsetse
infected environment even under improved environment [13].

Productivity indices of the muturu in different production
environments characterized by light and zero tsetse challenge
had been reported. The animals under a tsetse free environment
were found to perform better than those in a tsetse infected
environment. The productivity index varied from 36.8-72.3
under the two systems [13]. Age at puberty is an important
determinant of productive efficiency and herd size. According
to Peters [16] Puberty, expressed as the time of first oestrus
in the young female, is due to ovarian changes which are in
turn controlled by complex endocrinological events. In muturu
bull, Ezekwe [17] observed that under improved husbandry
and nutritional conditions, puberty was reported at an early
age of 11 months at a body weight of 87 kg. The study also
revealed that muturu bulls could be used for breeding from the
age of 15 months. Puberty was assumed to have occurred in
any heifer when plasma progesterone values reached/exceeded
/mg/mL [18,19]. The early maturity for breeding in the young
bulls and the heifers would ensure increase herd in the muturu
herds. Ezekwe and Kamalu [20] reported that muturu heifers
under improved management reach puberty at an early age of
12.25-14.60 months and weighed 90.50 kg and 85.20 kg for
supplemented and un-supplemented feeding respectively. It is
worth knowing that the relatively early attainment of puberty
by muturu heifers is higher than values obtained from other breeds of tropical cattle. Rakha et al. [21] reported that local
breeds of cattle in central Africa, namely; Angoni, Mashoma
and Afrikander attained puberty at about the age of 20, 19 and
20 months, respectively. Corresponding body weights of these
cattle breeds were 193 kg, 192 kg and 210 kg, respectively.

In Nigeria, Oyedipe et al. [22] reported that Sokoto gudali
heifers on a high plane of nutrition reached puberty at the age of
19 months, while those on medium and low planes did so at 21.3
and 23.5 months respectively. In Kenya, Ronningen et al. [23]
observed that Boran cattle reached puberty at the age of 16.6
months while McDowell [24] found that the age at puberty of
red sindhi cattle in India was 36.7 months. From these reports,
it is clear that there are considerable variations in age and body
weight at which different breeds of cattle attain puberty. Muturu
cattle breed is superior to most tropical breeds in reproductive
efficiency. It is well known that small temperate cattle breeds
attain puberty earlier than larger breeds [25]. Therefore the
relatively early attainment of puberty by muturu cattle which is
considerably a small breed indeed compared to larger tropical
cattle is consistent with observations in temperate cattle. This
is significant because in commercial production the age at
puberty in relation to the life span of the animal influences the
achievement of optimum reproductive performance of the breed
[26]. Early attainment of puberty also shortens the generation
interval, increase herd size as well as reduces the overhead cost
per animal. Exploitation of this important reproductive traits
of muturu cattle would therefore enhanced large herd size and
have significant effect on beef production and its availability in
Nigeria.

Herd size determines the level of selection and culling for genetic
improvement. Higher reproductive efficiency of the savanah
muturu under improve management will enhance large herd
size. The larger the herd size, the higher the number of animals
available for selection and replacement to maintain herd size.
Herd size determines selection intensity, selection accuracy and
genetic progress achieved through. The larger the herd size, the
higher the opportunities available for more genotypes in the
population to to express themselves for selection, culling and
the faster the selection response. It is in view of the importance
of herd size as it influences overall genetic progress due to
selection, that this study was designed to assess the savanah
muturu herd size and structure under rural farmers communities
as it influences or determines the number of animals available
for selection, culling and for replacement to maintain herd size.

Materials and Methods

Study area

The study was carried out in Taraba, Nasarawa, Kogi, Benue
and Niger states of Nigeria. In Benue the study was carried
out in five local government Areas of logo, Kwande, Buruku,
Ushongo and Tarka. Benue state is located within the lower
river Benue trough in the middle belt region of Nigeria. Its
geographic coordinates are longitude 7°47´ and 10°C 0´ East,
latitude 6°25´ and 8°C 8´ North. The state has extensive plains
of less than 150 m above sea level. The areas are flat to nearly
level and undulating with the eastern part of the state having an
altitude of the 1200 m above sea level. The climate of the area is the tropical climate with distinct wet and dry seasons. The
rainy season commences in April to October with mean annual
rainfall range of between 800–1500 mm. The temperature
fluctuates between 17. 6°C-37.0°C while relative humidity is
dependent on seasons but ranges from 50% to 80% being lowest
during the dry season and highest during the rainy season.

Ayilamo is a rural community settlement in Logo located at
a boundary between Wukari of Taraba State and Benue state.
And the study also includes some selected parts of Tarkaa local
government such as Mbaayogh, Mbakyagh–Mbahar council
ward. The community is located at latitude 70 461 21’’ N and
longitude 90 71 29’’ E with an altitude of 217 m. It has temperature
range of 24°–32°C, and a relative humidity of 65% to 82%,
precipitation of 35%-40%. The terrain in the environment is
generally very variable with Neutral soil pH. (5.5–8.5) there is
natural vegetation of tree cover making up 45%. The areas have
a management environment that is grass–land base (ranching)
with a mixed system of agriculture (crop and livestock). Animal
in these communities are confine mostly at night.

Experimental animals and their management

The animals that were used for the research were savannah
muturu cattle comprising both sexes and different ages. The
total number of the animals used for the research were 138,
comprising of 35 number of males and 103 number of females.
Out of the total number of the animals, thirty six (36) were calves,
nineteen (19) were breeding bulls, 56 were breeding cows and
twenty seven (27) were heifers. There was no castrated bull
among all the samples. The populations were drawn from Logo
and Tarka local government area of Benue State. The animals
were managed under free range with no supplementary feeding,
there is no evidence of veterinary care for the animals.

Experimental procedure and materials used

The study was carried out in two phases. In phase one, a
survey by use of questioner was administered to rural farming
communities that were associated with rearing of savanah
muturu cattle. Phase two was a field study having identified
muturu rearing communities in phase one. A One on one
discussion and oral interview of farmers who were reported to
had reared the muturu cattle but had no animals during the study
was also carried out. The reasons for discontinuing the rearing
of muturu cattles were sought. Rural farmer communities that
had muturu animals on ground, physical assessment of body
coat colour, individual herd size, herd composition, attempt
to control inbreeding by use of castration, economics of
production, health challenges, loses due to mortality (age group
most affected), attempt to retain heifers for replacement, use of
bulls of other breed (Bunaji) for serving the muturu dams were
information obtained from the muturu farmers. An inventory of
the entire population of savanah muturu cattle was also carried
out. Photographs of savanah muturu cattle were taken from
various herds using digital cameras. GPS Gadget were used to
identify the location of the herds.

Parameters that were measured

Population size of animals (Muturu cattle), herd sizes,
composition /herd proportion such as; number of breeding
males, number of breeding females, number of calves, number of castrated males or males not to be use for breeding and
number of replacement heifers. Phenotypic characterization
(presence or absence of horn, horn shape/orientation and coat
color were also assessed.

Data collection and analysis

Data were collected on morphological traits, individual herd
size, herd composition, attempt to control inbreeding by use of
castration, economics of production, health challenges, loses
due to mortality (age group most affected), attempt to retain
heifers for replacement, use of bulls of other breed (Bunaji) for
serving the muturu dams and population size. Data collected
were subjected to descriptive statistics and analysis of variance
to measure the effects of the parameters listed above.

Results

Herd size and composition in logo local government area
of Benue state

Table 2. Herd Size and composition of the Savannah Muturu under rural farmers in Tarka (North) Local Government Area.

Variables

Mean

± SE

Herd Size

3.60

0.73

Males

0.50

0.27

Females

3.10

0.55

Calves

1.00

0.26

Br. Bulls

0.30

0.15

Br. Cows

1.50

0.31

Cas. Bulls

0.00

0.00

Heifers

0.80

0.29

SE: Standard Error; Br: Breeding; Cas: Castrated.

Herd size and composition of savanah muturu in Ushongo
local government area of Benue state

In Ushongo Local Government Area, mean herd size was 3.00 ±
2.00, while the average number of males and females were 3.00
± 0.09 and 1.50 ± 0.50 respectively. Heifers were not available
for replacement. Unwanted bulls were not castrated (Table 3).

Table 3. Herd size and composition of the savanah Muturu in Kwande local government area of Benue State.

Discussion

Herd size of the savanah muturu in Nigeria

In all the surviving populations of the savanah muturu, the herd
sizes were very low. There were also no attempts to minimize
inbreeding as unwanted bulls were not castrated nor exchange
of bulls between farmers was not practiced. There were also no
designed efforts to retain heifers for replacement. Therefore,
there is no doubt that these populations had gone through high
levels of inbreeding. This was indicated by the high levels of
solid colors between and within the populations. Herd size has
direct correlation with the level of inbreeding, where herd sizes
were small, there would be a high level of inbreeding which
in turn would lead to inbreeding depression. A simulation of
herd dynamics proved that the rate of growth of the herd peaks
when female calves dominate the kraal [27]. The young animal
contributed about 50% of the herd size with more females (35%)
than males (15%).

Herd composition and characteristics of the savanah
muturu in Nigeria

The ratio of calves of one calf to a cow and the bull that
provided animals for replacement was not obtainable in these populations. There were more breeding females than heifers in
the populations. This was so because, selection for sale were
higher for the bulls and growers than the breeding females.
The number of calf were also low as farmers were conscious
of herd size, that a breeding female was allowed in the herd
for longer time than bulls, heifers and growing bulls. A large
number of studies have been concerned with a possible effect
of the size of the herd on the pregnancy rate, it is concluded by
almost all investigators that the pregnancy rate decreased with
the size of the herd [1-6]. On the interval between parturition
and conception, it is concluded by De Kruit [6] that this interval
is shorter in larger herds than in small herds (Table 4).

Table 4. Herd size and characteristics of savanah Muturu in Buruku local Goernment Area of Benue State.

In all the populations, the number of breeding bull were very low.
This would likely have an effect on the rate of calf productivity.
An infected male for several heat periods may not be able to have
successful mattings that would result to pregnancy. Conception
rate and calving interval could be affected significantly under
this condition. The effect of inbreeding would also be more pronounce when a breeding bull is use for long time as practiced
by the rural savana muturu farmers. In matured animals the ratio
is generally much biased with a preponderance of the female
stock than males on the average, the female animals constituted
60 to 75% in each herd [28].

Number of breeding males in the herd of the savanah
muturu in Nigeria

In all the populations, the number of breeding bull were very low.
This would likely have an effect on the rate of calf productivity.
An infected male for several heat periods may not be able to have
successful mattings that would result to pregnancy. Conception
rate and calving interval could be affected significantly under
this condition. The effect of inbreeding would also be more
pronounce when a breeding bull is use for long time as practiced
by the rural savana muturu farmers. In matured animals the ratio
is generally much biased with a preponderance of the female
stock than males on the average, the female animals constituted
60 to 75% in each herd [28].

Number of breeding females, heifers for replacement and
castrated males in the herd of the savanah muturu in
Nigeria

The number of breeding females determines the calf crop in the
herd. The available heifers for replacement and maintenance of
herd size is also determine by the breeding females in the herd.
Calf crop were low and there were no heifers for replacement
in all the herds. The proportion of breeding cows in the herd
was 49.1% while the proportion of the breeding bulls was
6% [28]. The profitability of any cattle enterprise is highly
determined by the number of breeding cows and young females
in the herd [29]. Selection for genetic improvement was not
possible in these herds as culling was not possible. Castration
was not carried out on unwanted bulls in all the populations.
Castration would have allows for culling unwanted bulls from
the herd as well as control the rate of inbreeding. It may also
have allow the fattening of bulls for sale. Hence, a side effect
of inbreeding, there was no competitive pricing and prices as
there was no design attempt for value chain intervention and
value addition. Thus, pricing, prices and marketing outlet were
low. The economic of production was very low despite the high
cost of the muturu animal, and hence no economic driving force
for continued rearing of savanah muturu animals. This had
contributed immensely to the journey of this breed to extinction
(Table 5).

Table 5. Herd size and composition of the savanah Muturu in Ushongo local government area of Benue State.

Effect of herd size on genetic variation due to random
sampling and genetic drift

In small populations, allelic drift through random sampling will
reduce heterozygosity. This result agreed with the observation
reported by Maule [30] who had shown that the typical coat
color of the savannah muturu is black and white. The result is
also analogous with the one reported by Adebambo [13]. The
maintenance of genetic diversity in a herd is a function of the
genetic effective population size [31,32], which is defined as the
size of an idealized population that would experience the same
magnitude of random genetic drift as the population of interest
[33]. In small, populations allelic diversity is lost relatively
quickly through random genetic drift but heterozygosity is less
affected. Genetic drift is a strong force in small populations and
can result in rapid loss of genetic diversity [34].

Effect of herd size on rate of inbreeding and inbreeding
depression

Genetic concern that arises with small population is the potential
for inbreeding, which is the breeding of related individuals.
Inbreeding may reduce fertility, juvenile survival and lifespan.
In small population that are isolated inbreeding is inevitable.
Inbreeding occurs when mating of individuals that are more
closely related than random individuals from a population
[35]. Inbreeding causes a reduction in genetic variability which
in return is the basis of inbreeding depression which affects
fitness-related traits such as fertility, when recession alleles are
deleterious [35-37]. Inbreeding depression has been documented
in numerous animal species [38-41]. Two genetic mechanisms
have been proposed as the cause of inbreeding depression both
relate to the decrease in heterozygosity during the inbreeding
process. The dominance effects (the presence of deleterious
recessive alleles) are thought to account for a large proportion
of the breeding depression observed [41-46].

Effect of herd size on selection intensity for genetic
improvement

The rate of genetic change is proportional to selection accuracy.
Selection accuracy is based on choosing animals with the best
breeding value for the traits in question [47]. It is also reported
that as the size of herd increases, the number of animals rejected
in the selection process will also increases given room for the
best animals to be selected, hence, selection intensity will also
increase. As selection intensity increases, genetic change in the
population will occur more rapidly [47-57].

Conclusion and Recommendations

Conclusion

The muturu cattle even though possesses the potential to enhance
large herd size for effective selection and herd replacement, this
was not so with the muturu herds under rural farmers. The herd
sizes in the study populations were very low. There were more
breeding females than heifers for replacement in the populations.
The number of breeding bulls was very low; selection targeting
heifers and young bulls for replacement and change of breeding
males would not be possible with this populations. There is a
high potential for inbreeding in this populations. Fitness-related
traits like fertility, and heterozygosity will be greatly affected. It
is also not possible to advance genetic improvement strategies
with this population through selection. This is because there
would be no animals to maintain herd size if selection is to
be attempted. Selecting all the available animals will not only
reduce selection accuracy and intensity, but would also affect
selection progress achievable per generation [57-69].

Recommendations

The following recommendations were drawn from the study:

1. There is need for all the Muturu farmers to retain heifers and
young bulls to which selection can be applied for genetic
improvement.

2 Where the herd sizes are extremely low, there is need to
adopt bull exchange practices during breeding for genetic
improvement and to reduce rate of inbreeding depression.

References

Andesen H. The effect of season of the year, age of cow and size of the herd on fertility in cows. Arsberetn Inst Sterilites Research. 1966;227.

Lande R, Barrowdough GF. Effective population size, genetic variation and their use in population management pages 87-123 in M.E Soule editor .viable population for conservation .Cambridge University Press Cambridge England.1987.